Magnetic field lines form closed loops.

Magnetic field lines form closed loops.

• A. True
• B. False
• C. Never
• D. Sometimes

Answer: (A)

Magnetic field lines are continuous and have no start or end because there are no magnetic monopoles. This means the field must form closed loops in space. A handy way to see this is Gauss’s law for magnetism, which says the net flux through any closed surface is zero, so lines can’t begin or end at a magnetic charge. Around a bar magnet, lines leave the north pole, curve through space, and enter the south pole; inside the magnet they go from south back to north, completing the loop. Around a current-carrying wire, the field lines form concentric circles around the wire, and these circles can be considered parts of closed loops when extended through space. In all typical situations, magnetic field lines form closed loops, so the statement is true.

Magnetic field lines are continuous and have no start or end because there are no magnetic monopoles. This means the field must form closed loops in space. A handy way to see this is Gauss’s law for magnetism, which says the net flux through any closed surface is zero, so lines can’t begin or end at a magnetic charge.

Around a bar magnet, lines leave the north pole, curve through space, and enter the south pole; inside the magnet they go from south back to north, completing the loop. Around a current-carrying wire, the field lines form concentric circles around the wire, and these circles can be considered parts of closed loops when extended through space. In all typical situations, magnetic field lines form closed loops, so the statement is true.